1. Field of the Invention
The present invention relates to the technical field of image compression and, more particularly, to an image compression system for dynamically adjusting compression parameters by content sensitive detection in video signal.
2. Description of Related Art
With the rapid advance of electronics technologies and transmission techniques, the requirement for image quality in browsing is getting higher. Because the size of image data is usually huge, the image data is typically compressed for then being transferred to the Internet or stored in a hard disk. With image compression techniques, the memory space occupied by image data can be saved and the speed of transmission can thus be increased. Therefore, the image compression is currently very popular on research.
In March, 2003, the video compression standard H.264 is formally published by the ITU-T/ISO, which is known as a new-generation video encoding standard with an excellent performance in comparison with the previously used standard. Specially, as compared with H.263 or MPEG-4 on the same quality, the number of code rates can be reduced to half or, for the same code rate, the peak signal to noise ratio (PSNR) is significantly increased.
However, for the field of image display applications, the panel resolution is increased from the earliest QCIF (Quarter Common Intermediate Format) to ¼ high definition (Quarter High Definition, qHD) or even up to full high definition (Full HD) or 4K2K. Accordingly, in case that there is no suitable compression or other technique provided at the front-end, the power, bandwidth and timing rate required for data transmission are inevitably increased.
For increasing the compression efficiency, H.264 video compression standard provides a variable block size in inter coding. In the prior art, such as U.S. Pat. No. 5,021,891 granted to Lee for an “Adaptive block size image compression method and system”, it is based on the magnitude of an image texture change to determine how to segment the 16×16 block used in a current compression. However, in a hardware implementation, such technique has to first test multiple sizes of blocks in parallel and estimate the number of bits required for each combination, and then determine the segmentation on the blocks. Thus, the hardware cost is too high and thus it is not appropriate for a hardware implementation of real-time compression/decompression.
Therefore, it is desirable to provide an improved image compression system to mitigate and/or obviate the aforementioned problems.